diff --git a/lib/capybara/selector/builders/css_builder.rb b/lib/capybara/selector/builders/css_builder.rb
index a116e58f..9d612992 100644
--- a/lib/capybara/selector/builders/css_builder.rb
+++ b/lib/capybara/selector/builders/css_builder.rb
@@ -38,7 +38,7 @@ module Capybara
             attribute_conditions(class: classes)
           else
             cls = Array(classes).group_by { |cl| cl.start_with?('!') && !cl.start_with?('!!!') }
-            (cls[false].to_a.map { |cl| ".#{Capybara::Selector::CSS.escape(cl.sub(/^!!/,''))}" } +
+            (cls[false].to_a.map { |cl| ".#{Capybara::Selector::CSS.escape(cl.sub(/^!!/, ''))}" } +
             cls[true].to_a.map { |cl| ":not(.#{Capybara::Selector::CSS.escape(cl.slice(1..-1))})" }).join
           end
         end
diff --git a/lib/capybara/selector/builders/xpath_builder.rb b/lib/capybara/selector/builders/xpath_builder.rb
index 897065c0..a491110e 100644
--- a/lib/capybara/selector/builders/xpath_builder.rb
+++ b/lib/capybara/selector/builders/xpath_builder.rb
@@ -33,7 +33,7 @@ module Capybara
               if klass.start_with?('!') && !klass.start_with?('!!!')
                 !XPath.attr(:class).contains_word(klass.slice(1..-1))
               else
-                XPath.attr(:class).contains_word(klass.sub(/^!!/,''))
+                XPath.attr(:class).contains_word(klass.sub(/^!!/, ''))
               end
             end.reduce(:&)
           end
diff --git a/lib/capybara/selector/selector.rb b/lib/capybara/selector/selector.rb
index 642a9d97..2e8d4b55 100644
--- a/lib/capybara/selector/selector.rb
+++ b/lib/capybara/selector/selector.rb
@@ -227,12 +227,7 @@ module Capybara
     # @return [#call]                             The block that will be called to generate the XPath expression
     #
     def xpath(*allowed_filters, &block)
-      if block
-        @format, @expression = :xpath, block
-        allowed_filters = parameter_names(block) if allowed_filters.empty?
-        allowed_filters.flatten.each { |ef| expression_filters[ef] = Filters::IdentityExpressionFilter.new(ef) }
-      end
-      format == :xpath ? @expression : nil
+      expression(:xpath, allowed_filters, &block)
     end
 
     ##
@@ -250,12 +245,7 @@ module Capybara
     # @return [#call]                             The block that will be called to generate the CSS selector
     #
     def css(*allowed_filters, &block)
-      if block
-        @format, @expression = :css, block
-        allowed_filters = parameter_names(block) if allowed_filters.empty?
-        allowed_filters.flatten.each { |ef| expression_filters[ef] = Filters::IdentityExpressionFilter.new(ef) }
-      end
-      format == :css ? @expression : nil
+      expression(:css, allowed_filters, &block)
     end
 
     ##
@@ -465,6 +455,15 @@ module Capybara
     def parameter_names(block)
       block.parameters.select { |(type, _name)| %i[key keyreq].include? type }.map { |(_type, name)| name }
     end
+
+    def expression(type, allowed_filters, &block)
+      if block
+        @format, @expression = type, block
+        allowed_filters = parameter_names(block) if allowed_filters.empty?
+        allowed_filters.flatten.each { |ef| expression_filters[ef] = Filters::IdentityExpressionFilter.new(ef) }
+      end
+      format == type ? @expression : nil
+    end
   end
 end
 
diff --git a/spec/selector_spec.rb b/spec/selector_spec.rb
index 146ac11b..20235f01 100644
--- a/spec/selector_spec.rb
+++ b/spec/selector_spec.rb
@@ -253,7 +253,7 @@ RSpec.describe Capybara do
           expect(string.all(:custom_xpath_selector, XPath.descendant(:div, :p), class: ['!cc', '!dd', 'bb']).size).to eq 1
         end
 
-        it 'handles classes starting with ! by requiring negated negated first', :focus_ do
+        it 'handles classes starting with ! by requiring negated negated first' do
           expect(string.all(:custom_css_selector, 'div, p', class: ['!!!mine']).size).to eq 1
           expect(string.all(:custom_xpath_selector, XPath.descendant(:div, :p), class: ['!!!mine']).size).to eq 1
         end